Pipe-cutting and chamfering arrangement

ABSTRACT

The invention pertains to a device for cutting and chamfering thin-walled pipes. In order to cut and chamfer a pipe, a drive unit with tools arranged on its shaft is manually guided around a pipe that is clamped in a vise by means of clamping jaws with a semicircular contact surface. The tools, namely a saw blade and a milling cutter, are arranged one behind the other on the shaft. The saw blade is provided with a depression, into which the milling cutter is inserted such that the outer edge of the milling cutter is protected.

FIELD OF THE INVENTION

The invention pertains to a device for cutting and chamfering pipes.

BACKGROUND

A device for cutting pipes is known from CH 568,117. In this case, adriving motor with a saw blade is advanced by means of an eccentricarrangement of different rings. Subsequently, the driving motor with thesaw blade is manually guided around the pipe such that said pipe is cut.The pipe is centered and held in a vise by means of two V-shapedclamping jaws.

When welding a pipe to another pipe by means of an automated orbitalwelding process, an exact and uniform chamfer must be produced on bothpipe ends. Otherwise, the welding process cannot be carried outcorrectly. This means that the pipe must be chamfered in one additionalprocessing step after it has been cut.

For this purpose, the aforementioned device is equipped with anauxiliary milling cutter. This auxiliary milling cutter is arrangeddirectly adjacent to the saw blade. The driving motor with the saw bladeand the auxiliary milling cutter is guided around the stationary pipeonce such that the pipe is simultaneously cut and chamfered.

One disadvantage of this device is that an exact chamfer cannot beproduced in thin-walled pipes with large diameters because the clampingjaws of the pipe receptacle only accommodate the pipe in pointwisefashion. This means that the thin-walled pipe is clamped in the viseoff-center during the clamping process.

Another problem of the aforementioned device is that the auxiliarymilling cutter is very susceptible to wear on its front edge, i.e., theouter edge of the auxiliary milling cutter.

The pipe end also must be chamfered if a press fitting with a rubberring seal is attached. These press fittings are used for connecting twothin-walled pipes of special steel in drinking water installations. Inthis case, two different chamfers are produced on the pipe ends, i.e., asteep chamfer for attaching and centering the press fitting onto thepipe and a flat chamfer.

SUMMARY OF THE INVENTION

The invention is based on the objective of developing a device forcutting and chamfering pipes which makes it possible to cut and exactlychamfer thin-walled pipes.

The advantage of the invention is that thin-walled pipes can be pressedinto a round shape, cut and correspondingly chamfered in one processingstep.

Due to the special design of the saw blade, the milling cutter has asignificantly longer service life.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail below with reference to theFigures. Shown are:

FIG. 1, a side view of a device for cutting and chamfering pipesaccording to the invention with a clamping device and a machine toolunit;

FIG. 2a, a top view of the partially sectioned clamping device;

FIG. 2b is a view of a clamping jaw;

FIG. 3, a top view of the machine tool unit;

FIG. 4, an enlarged representation of the tools shown in FIG. 1, and

FIG. 5, a top view of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The Figures show a device for cutting and chamfering pipes. This deviceconsists of a clamping device 1 and a machine tool unit 2.

FIGS. 2a and 2b show that the clamping device 1 consists of a vise 3.The holders 5 and 6 for the clamping jaws can be displaced relative toone another by means of a spindle 4. Clamping jaws 7 and 8 are rigidlyconnected to the respective clamping jaw holders 5 and 6. The clampingjaws have a semicircular inner surface 9 that adjoins the outer surfaceof a pipe 10 during the clamping process. When clamping a thin-walledpipe, oval sections of the pipe are compensated for by the clampingjaws.

When processing pipes of different diameters, the clamping jaws must bereplaced with other clamping jaws with a semicircular inner surface thatcorresponds to the outer surface of the respective pipe. Thisreplacement is realized by loosening the screws 11 that serve for fixingthe clamping jaws to the clamping jaw holders. In addition, othersolutions may be considered for attaching the clamping jaws, e.g., theutilization of a quick-action clamping system with a toggle leverarrangement.

A nonhardened material, in this case GGG 40, is used as the material forthe clamping jaws 7 and 8. The semicircular inner surface of theclamping jaws is produced by mechanical processing so as to attain anexact inner contour with very small tolerances.

FIG. 3 shows the function of the device for cutting and chamferingpipes. The machine tool unit 2 comprises a drive unit 30. The tools 15and 16 for processing the pipes are arranged on the shaft 17 of thedrive unit.

The drive unit 30 is fastened on an eccentric ring 33. The eccentricring 33 is rotatably arranged on the inner surface of a guide ring 31.The outer surface of the guide ring 31 is rotatably arranged on anannular guide housing 32. The center of motion of this bearingarrangement is identical to the center of the pipe. The drive unit isadvanced via the eccentric ring 33. The depth of advance is limited bymeans of an adjustable limit stop 34 on the guide ring and a driver pin35 of the eccentric ring 33. After the eccentric advance is carried out,the drive unit with the tools is manually guided around the pipe onceconcentric to the pipe center.

The aforementioned advance may also be realized in the form of a linearadvance, e.g., with the aid of a spindle and a corresponding cradleguide.

An exact advance is essential for all embodiments because the tolerancesof the chamfers are usually very small in thin-walled pipes.Consequently, it is advantageous to arrange an exact graduated scale 36on the guide ring so as to allow a precise adjustment of conventionalpipe dimensions. A marking 37 that cooperates with the graduate scale 36is arranged on the adjustable limit stop 34. The marking 37 may berealized in the form of a vernier. In addition, visual aids may be usedfor attaining a more precise adjustment.

FIGS. 4 and 5 show the arrangement of a saw blade 15 and a millingcutter 16 on the shaft 17 of the drive unit 30. The saw blade 15 has anaxial depression 18 of larger diameter than the outer diameter of themilling cutter 16. The milling cutter 16 is inserted into thisdepression 18. The outer edge 19 of the milling cutter is covered by thesaw teeth 20. This region is not engaged during the machining process.Consequently, the milling cutter is subjected to less wear. Even thesmallest chips can no longer penetrate between the contact surfaces ofthe milling cutter and the saw blade and spread apart both tools. Untilnow, this spreading apart of the tools frequently resulted in theirdestruction.

The milling cutter 16 is realized in the form of a chamfering cutter.Certain chamfering cutters can be used depending on the respectiverequirements. When attaching press fittings, it is advantageous toarrange two different chamfers on the pipe ends. This requires achamfering cutter that can produce two chamfers. This is attained due tothe geometric design of the milling cutter 16. FIG. 4 shows that thecutting edge 22 of the milling cutter comprises an initial bevel 23 ofapproximately 45° and a subsequent bevel 24 of approximately 5°-20°relative to the longitudinal axis 21 of the pipe. The milling cutter mayhave any arbitrary geometry, but the outer edge of the milling cutter isalways protected by the depression 18 in the saw blade.

FIG. 5 shows that the milling cutter 16 has only an insignificantlysmaller diameter than the saw blade 15. In this embodiment, the radiusis smaller by approximately the depth of advance of the saw blade. Thedepth of advance of the saw blade is approximately 1.5-times the wallthickness 29 of the pipe. In contrast to thick-walled pipes, the sawblade is engaged slightly behind the inner pipe wall when cuttingthin-walled pipes. Consequently, more saw teeth 20 are engaged andrattling is prevented. Subsequently, the milling cutter must immediatelyengage because the saw blade would otherwise protrude excessively farinto the pipe.

What is claimed is:
 1. A device for cutting and chamfering a pipecomprising:a drive unit having a shaft; a processing tool arranged onthe shaft, the processing tool comprising a cutting tool and achamfering tool arranged one behind the other, the chamfering toolhaving an outer diameter, the cutting tool having an axial depressiondefined therein, the axial depression having a diameter greater than theouter diameter of the chamfering tool and the chamfering tool beingarranged in the depression; and a clamping device with clamping jaws foraccommodating the pipe, each of the clamping jaws having a partiallycircular cross section; wherein the drive unit and the processing toolare concentrically guided around the pipe that is clamped in theclamping device.
 2. Device for cutting and chamfering a pipe accordingto claim 1, wherein the clamping jaws are detachable from the clampingdevice for replacement.
 3. Device for cutting and chamfering a pipeaccording to claim 1, wherein the clamping jaws are manufactured of anonhardened material.
 4. Device for cutting and chamfering a pipeaccording to claim 1, wherein the partially circular cross section ofthe clamping jaws has an inscribed angle between 160° and 180°.
 5. Adevice for cutting and chamfering a pipe comprising:a drive unit havinga shaft; a processing tool arranged on the shaft, the processing toolcomprising a cutting tool and a chamfering tool arranged one behind theother, the chamfering tool having an outer edge and an outer diameter,the cutting tool having an axial depression defined therein, thechamfering tool being arranged in said axial depression, the axialdepression having a diameter greater than the outer diameter of thechamfering tool, the cutting tool further having teeth that cover theouter edge of the chamfering tool so that during chamfering, the outeredge of the chamfering tool is not used; and a clamping device withclamping jaws for accommodating the pipe, each of the clamping jawshaving a partially circular cross section; wherein the drive unit andthe processing tool are concentrically guided around the pipe that isclamped in the clamping device.
 6. Device for cutting and chamfering apipe according to claim 5, wherein the clamping jaws are detachable fromthe clamping device for replacement.
 7. Device for cutting andchamfering a pipe according to claim 5, wherein the clamping jaws aremanufactured of a nonhardened material.
 8. Device for cutting andchamfering a pipe according to claim 5, wherein the partially circularcross section of the clamping jaws has an inscribed angle between 160°and 180°.